#include "urlencode.h"
#include "common.h"
#include "stringutils.h"

static int HexPairValue(const char * code)
{
	int value = 0;
	const char * pch = code;
	for (;;)
	{
		int digit = *pch++;
		if (digit >= '0' && digit <= '9') 
			value += digit - '0';		
		else if (digit >= 'A' && digit <= 'F') 
			value += digit - 'A' + 10;		
		else if (digit >= 'a' && digit <= 'f') 
			value += digit - 'a' + 10;		
		else 
			return -1;

		if (pch == code + 2)
			return value;
		value <<= 4;
	}
}

int InternalUrlDecode(const char *source, char *dest,
	bool encode_space_as_plus)
{
	char * start = dest;

	while (*source)
	{
		switch (*source)
		{
		case '+':
			if (encode_space_as_plus) 
				*(dest++) = ' ';
			else 
				*dest++ = *source;			
			break;
		case '%':
			if (source[1] && source[2]) {
				int value = HexPairValue(source + 1);
				if (value >= 0) {
					*(dest++) = value;
					source += 2;
				}
				else {
					*dest++ = '?';
				}
			}
			else {
				*dest++ = '?';
			}
			break;
		default:
			*dest++ = *source;
		}
		source++;
	}

	*dest = 0;
	return static_cast<int>(dest - start);
}

int UrlDecode(const char *source, char *dest)
{
	return InternalUrlDecode(source, dest, true);
}

int UrlDecodeWithoutEncodingSpaceAsPlus(const char *source, char *dest)
{
	return InternalUrlDecode(source, dest, false);
}

bool IsValidUrlChar(char ch, bool unsafe_only)
{
	if (unsafe_only) {
		return !(ch <= ' ' || strchr("\\\"^&`<>[]{}", ch));
	} else {
		return isalnum(ch) || strchr("-_.!~*'()", ch);
	}
}

int InternalUrlEncode(const char *source, char *dest, unsigned int max,
	bool encode_space_as_plus, bool unsafe_only)
{
	static const char *digits = "0123456789ABCDEF";
	if (max == 0) {
		return 0;
	}

	char *start = dest;
	while (static_cast<unsigned>(dest - start) < max && *source) {
		unsigned char ch = static_cast<unsigned char>(*source);
		if (*source == ' ' && encode_space_as_plus && !unsafe_only) {
			*dest++ = '+';
		} else if (IsValidUrlChar(ch, unsafe_only)) {
			*dest++ = *source;
		} else {
			if (static_cast<unsigned>(dest - start) + 4 > max) {
				break;
			}
			*dest++ = '%';
			*dest++ = digits[(ch >> 4) & 0x0F];
			*dest++ = digits[       ch & 0x0F];
		}
		source++;
	}
	ASSERT(static_cast<unsigned int>(dest - start) < max);
	*dest = 0;

	return static_cast<int>(dest - start);
}

int UrlEncode(const char *source, char *dest, unsigned max) {
	return InternalUrlEncode(source, dest, max, true, false);
}

int UrlEncodeWithoutEncodingSpaceAsPlus(const char *source, char *dest,
	unsigned max) {
		return InternalUrlEncode(source, dest, max, false, false);
}

int UrlEncodeOnlyUnsafeChars(const char *source, char *dest, unsigned max) {
	return InternalUrlEncode(source, dest, max, false, true);
}

std::string InternalUrlDecodeString(const std::string & encoded,
	bool encode_space_as_plus)
{
	size_t needed_length = encoded.length() + 1;
	char* buf = STACK_ARRAY(char, needed_length);
	InternalUrlDecode(encoded.c_str(), buf, encode_space_as_plus);
	return buf;
}

std::string UrlDecodeString(const std::string & encoded)
{
	return InternalUrlDecodeString(encoded, true);
}

std::string UrlDecodeStringWithoutEncodingSpaceAsPlus(
	const std::string & encoded)
{
	return InternalUrlDecodeString(encoded, false);
}

std::string InternalUrlEncodeString(const std::string & decoded,
	bool encode_space_as_plus, bool unsafe_only)
{
	int needed_length = static_cast<int>(decoded.length()) * 3 + 1;
	char* buf = STACK_ARRAY(char, needed_length);
	InternalUrlEncode(decoded.c_str(), buf, needed_length,
		encode_space_as_plus, unsafe_only);
	return buf;
}

std::string UrlEncodeString(const std::string & decoded)
{
	return InternalUrlEncodeString(decoded, true, false);
}

std::string UrlEncodeStringWithoutEncodingSpaceAsPlus(
	const std::string & decoded)
{
	return InternalUrlEncodeString(decoded, false, false);
}

std::string UrlEncodeStringForOnlyUnsafeChars(const std::string & decoded)
{
	return InternalUrlEncodeString(decoded, false, true);
}